You can get a Mikrotik router and attach a 3g / evdo card to it. Then add a wifi card as well. Then you can setup routing / bridging and it’s all good.
you would face a lot of technical problems: 3g coverage, packet loose and high latency when the vehicle is in motion, constant power supply, re-connection when the ppp is disconnected, etc…
it is not just plug the gear and go..